Field of the Invention
The present invention relates to an automatic transmission for a vehicle.
Description of Related Art
Recent increases in oil prices are triggering stiff competition in enhancing fuel consumption of a vehicle.
In this sense, research for an engine has been made to achieve weight reduction and to enhance fuel consumption by so-called downsizing and research on an automatic transmission has been performed to simultaneously provide better drivability and fuel consumption by achieving more shift stages.
However, in order to achieve more shift stages for an automatic transmission, the number of parts is typically increased, which may deteriorate installability and/or power flow efficiency and may increase production cost, and weight.
Therefore, in order to maximally enhance fuel consumption of an automatic transmission having more shift-stages, it is important that better efficiency is derived by less number of parts.
In this respect, an eight-speed automatic transmission has been introduced recently and a planetary gear train for an automatic transmission enabling more shift-stages is under investigation.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.